I think here you are making an argument that Darcy felt lust for Elizabeth, rather than infatuation (or true love). Am I right?

I'd like to say that, while most red-blooded males experience physical attraction, they also tend to experience in at least one point in their lives, an emotion they at least describe as love. Sexuality is not necessarily separate from love, there are plenty of babies born to happily-married couples, including cases where I know the husband made a number of sacrifices for his wife (and vice-versa). :)

Darcy describes his own feelings for Elizabeth as love: You must allow me to tell you how ardently I admire and love you." (chpt 34)

He also does seem to respect Elizabeth on an intellectual level before the proposal:
"You are perfectly right. You have employed your time much better. No one admitted to the privilege of hearing you can think anything wanting. We neither of us perform to strangers." (chpt 31)
"You cannot have a right to such very strong local attachment. You cannot have been always at Longbourn." (chpt 32 - this passage is generally interpreted as Darcy thinking that Elizabeth must have been influenced by someone better than her parents). These indicate some respect for Elizabeth's intellectual abilities.

In their conversations, he is not trying to "top" her witticisms, he replies in similar terms, but not in a way that seeks to intellectually dominate and intimidate her, instead Darcy more opens up in response to Elizabeth's teasing:
"I am perfectly convinced by it that Mr. Darcy has no defect. He owns it himself without disguise."

"No," said Darcy, "I have made no such pretension. I have faults enough, but they are not, I hope, of understanding. My temper I dare not vouch for. (chpt 11)